1. Field of the Invention
The invention relates to a cover device, more particularly to the cover device of a storage battery.
2. Description of the Related Art
Referring to FIG. 1, a conventional storage battery is shown to comprise a container (1) that has a plurality of separate rectangular-shaped compartments (11) for receiving electrodes and a main cover (2) provided securely on the container (1) to close a top portion of the container (1). As best illustrated in FIG. 2, the main cover (2) confines a space (26) therein and has a flat bottom which is formed with a plurality of inlet-holes (23) therethrough for filling an electrolytic solution, such as dilute sulfuric acid, into the separate compartments (11) and a plurality of sub-cover units (25) for closing the inlet-holes (23). The main cover (2) further has a plurality of gas inlets (24) which are also formed in the flat bottom and which permit the gas that is produced in each of the compartments (11) to flow into the space (26) and out of a gas outlet (27) which extends outside the periphery of the main cover (2).
During mass production, a sheath (28) is provided hermetically on a free end of the gas outlet (27) and the inlet-holes (23) of the main cover (2) are sealed by aluminum foils (not illustrated) with the use of a hot melting process. Thus, the metal plates inside the storage battery are isolated from the exterior of the same so as to prevent oxidation action within the storage battery.
In use, the aluminum foils are removed first so as to permit pouring of the dilute sulfuric acid into the respective compartments (11) via the inlet-holes (23) of the main cover (2). The inlet-holes (23) are closed by the sub-cover units (25) after the filling operation. However, the user often forgets to remove the sheath (28) that seals hermetically the free end of the gas outlet (27) of the main cover (2). Thus, when the storage battery is electrically connected so as to provide light, the flow of current inside the storage battery causes electrolysis, i.e., bubbles of gas are produced on the electrodes. The gas accumulates within the storage battery and cannot escape to an exterior of the same through the gas inlets (24), the space (26) and the gas outlet (27). The accumulated gas eventually leads to an explosion and may endanger the persons nearby.